1. Field of Invention
The present invention relates to a bi-stable projection screen, and more particular, relates to a bi-stable projection screen integrating a light diffusion element and a bi-stable display element, and capable of displaying a pattern in addition to be used in projection imaging.
2. Related Art
A projection screen is mainly divided into two types, namely a reflective projection screen and a transmissive projection screen. A projection screen of the reflective projection screen may reflect a projection light and enable the reflected light to produce a light diffusion. A main light path thereof is defined by an image projected onto the projection screen by a projector, and then reflected and diffused into eyes of viewers. This type of projection screen mainly includes two kinds, namely an ordinary screen and a glass beaded screen. The ordinary screen is fabricated by spraying a white paint on a special substrate and then performing a simple process. The ordinary screen is mainly advantageous in a cheap price, wide viewing angle, and soft image color, but has lower reflected brightness and is not easy to exhibit an image with higher definition. Thus, the ordinary screen is usually used in small and medium places. The glass beaded screen is fabricated by uniformly spraying micro glass beads on a special substrate, and thus has advantages of a wide viewing angle and a high brightness. Such a reflective projection screen is used in an orthographic projection (front projection) situation, mainly in cinemas, conference rooms, meeting halls, living rooms, and so on. The front projection screen generally has a larger area and a single tone, typically white or light gray.
The aforementioned transmissive projection screen makes a light projected by a projector to pass through and be diffused. A main light path thereof is defined by an image projected on the projection screen by the projector, and then diffused and transmitted into eyes of the viewers. The main applications of the transmissive projection screen include rear projection TVs, display screens in conference rooms, bulletin boards in shopping malls, and so on. The aforementioned two screens may achieve the projection light diffusion effect on the screens in use, but they would produce an inharmonious visual feeling with the surrounding environment when not used. The front projection screen is usually a flexible screen and can be furled. The rear projection screen is usually a rigid screen and is hard to be packed, so it is more inharmonious with the overall interior design.